1. Key Management/ Infrastructures Security 07

2. 2 Basic problem Cryptographic security: must be some keys that are not cryptographically protected. Must find other ways to protect these keys.

3. 3 How can the system identify you? Passwords –Something you know Hardware –Something you have Biometrics –Something you are

4. 4 Password A sequence of characters known to only user and system, fx –QWERTY –8676 –Cis#1isT$

5. 5 Attacks/aspects Steal from systemStorage by system Steal password from owner Storage by owner Steal password while it is used Use of password Guess passwordChoice of password AttacksAspects

6. 6 Choice of password Keyspace: long passwords = many possibilities –4-digit PIN-code: 10.000 possibilities –Unix password:  2 52 Practical limit –Max remember 12 characters under pressure

7. 7 Passphrases Length not enough – quality matters Passphrases: –Course in security number 1 is Top-dollar –Cis#1isT$ As hard to guess as random passwords! If users don’t do as they are told? - Programs rejecting bad passwords. Or programs that help estimate quality.

8. 8 Guessing a password Simply attempt to log on until you succeed. After 3 attempts, block account  ?! –Good if attacker wants to log in –Bad if purpose is denial of service. –Better with delays after failed attempts.

9. 9 Steal password under transmission Look over the shoulder –Physically – or electronically: Spyware Fake hardware Network eavesdropping Solutions involve –Cryptography –Hardware –Biometrics

10. 10 Steal password from user If it’s written down? –Piece of paper in dust bin Devices for remembering PIN-codes can help BUT: Social engineering…

11. 11 Social engineering 336 students were asked by mail to send back their passwords to validate the password database 138 returned their passwords!! A few changed their passwords, but no one reported to the system administrator Passwords for chocolate ?!

12. 12 More (less?) sophisticated methods: Call the company Naive software solutions: ”I’m security administrator at IBM, the software you delivered has a problem, I need your password…” Phising: send mails leading people to fake web pages: we need to validate your account, click here – and enter your password..

13. 13 Social engineering – defenses? One of the most effective ways to break into systems Information and education Technology: make sure it takes more than you can steal by phising.. –Hardware –Biometrics

14. 14 Stealing passwords from systemet Password-database in cleartext  Better method: store a complicated function of password and not the password itself. No guarantee: with badly chosen passwords, this may also fail.

15. 15 Password-DB by one-way functions Table with entries: –U, user –f(password of U) Where f is a function that is easy to compute but hard to invert. No immediate information on passwords in table. Nevertheless, an entered password can be checked.

16. 16 Dictionary attack One-way function is known Take a table of likely passwords. For each pw in table, compute f(pw) until match is found Up to 25% succes-rate in practice –Better choice of passwords - passphrases

17. 17 Passwords - overview AspectAttackDefense ChoiceGuess Dictionary Passphrases Help to choose UsageSpyware, eavesdropping, … Training Hardware, biometrics, crypto User storageSocial engineeringTraining System storage”Steal DB” Dictionary One-way functions Better choice of pw

18. 18 Hardware Not just: prevent exposure of keys. But also: Make sure your key exists in only one copy –easy to copy files, or magnetic stripe cards –If copying hard, or takes time, better chance that theft is detected Means hardware can be useful even if break- in possible

19. 19 Chip-card Cards with computer on board –CPU, RAM, I/O, even RSA co-processor Fx the new DanKort, SIM-cards for mobile phones … Physical intrusion not impossible, but hard..

20. 20 Always necessary to break in? – Analysis of current usage Naiv implementation pf RSA-encryption –Scan bits in key one by one: If 0, one set of instructions If 1, another –Very big difference in current usage of the two –Measure current usage, plot => private-key in cleartext!

21. 21 Tamper resistance American standard: FIPS Must detect –Cooling –Shaking –Explosion –Magnetic fields –…

22. 22 An example IBM 4758 Evaluated to max FIPS- level Used by many banks No known attacks on physical protections – but attacks on API previously

23. 23 Authenticity – again(!) Scenario: –RSA private-key in IBM4758, can only be accessed with smart card and PIN code. Via software you download (applet) you instruct system to sign document. But what is actually signed?!

24. 24 Hardware - overview Protection – tamper-proof – or: – tamper -evident. Attacks –Bad API’s –Unforseen sideeffect –Control over both hard- and software?

25. 25 Biometrics Traditionally: –Man-man –Based on signatures, photos, etc. Here: –Man-machine –Based on measurement of physical characteristics BornholmsTrafikken

26. 26 General Solution Function from individual to data –Based on particular biological characteristics –Database on these Identifikation: –Measure –(Re-)calculate function –Compare to database

27. 27 False negatives and positives False negative: rejected, even though you are a legal user False positive: approved, although you shouldn’t be. Cannot be completely avoided. What is acceptable is decided by application.

28. 28 Technology Iris-scanning Fingerprint Face shape Handgeometry Speach … Often the first two are best

29. 29 Pro’s and Con’s You always bring yourself But: Anonymity, privacy May be other ways to get in than by imitating the physical characteristics Natural physical change of user. Note: Your fingerprint is not a signature! Biometrics good for access control to your signature key, but cannot replace it

30. 30 Key management - overview Password (knows) Biometrics (is) Hardware (has) Key

31. 31 Have seen ways for system to identify who wants access to something (here a key) Must prevent access without being approved by system Need ways to ”lock up” the ressource.. A remaining question

32. 32 Two ways to ”lock it up” If secure hardware around, easy If not, must go back to crypto Ex: key to be protected by password without hardware security – must encrypt key under password Problem: can test all passwords. Solution: slow the process down.